1,857 research outputs found
A Trichomycete-like Fossil from the Triassic of Antarctica
No abstract is available for this item
Palaeofibulus Gen. nov., a Clamp-Bearing Fungus from the Triassic of Antarctica
No abstract is available for this item
New species, phylogeny, host-associations and geographic distribution of genus Cryptosporella (Gnomoniaceae, Diaporthales)
The phylogeny of Cryptosporella is revised to include recently discovered species. Eight species new to science are described and two new combinations are proposed, raising the total number of species accepted in Cryptosporella to 19. The species delimitation and phylogeny for Cryptosporella are determined based on analyses of DNA sequences from three genes (btubulin, ITS and tef1-a), comparative morphology of sexual structures on their host substrate, and host associations. The inferred phylogeny suggests that Cryptosporella has speciated primarily on Betulaceae with 16 species occurring on hosts in that plant family. The host range of most species seems to be narrow with nine species reported from a single host species or subspecies and seven species occurring on plants within a single host genus. A key to species is provided. The known distribution of Cryptosporella is expanded to mountain cloud forests of the provinces of ChiriquıŽ in Panama and TucumaŽn in Argentina.The phylogeny of Cryptosporella is revised to include recently discovered species. Eight species new to science are described and two new combinations are proposed, raising the total number of species accepted in Cryptosporella to 19. The species delimitation and phylogeny for Cryptosporella are determined based on analyses of DNA sequences from three genes (btubulin, ITS and tef1-a), comparative morphology of sexual structures on their host substrate, and host associations. The inferred phylogeny suggests that Cryptosporella has speciated primarily on Betulaceae with 16 species occurring on hosts in that plant family. The host range of most species seems to be narrow with nine species reported from a single host species or subspecies and seven species occurring on plants within a single host genus. A key to species is provided. The known distribution of Cryptosporella is expanded to mountain cloud forests of the provinces of ChiriquıŽ in Panama and TucumaŽn in Argentina
A proposed mechanism for nitrogen acquisition by grass seedlings through oxidation of symbiotic bacteria
In this paper we propose and provide evidence for a mechanism, oxidative nitrogen scavenging (ONS), whereby seedlings of some grass species may extract nitrogen from symbiotic diazotrophic bacteria through oxidation by plant-secreted reactive oxygen species (ROS). Experiments on this proposed mechanism employ tall fescue (Festuca arundinaceae) seedlings to elucidate features of the oxidative mechanism. We employed 15N2 gas assimilation experiments to demonstrate nitrogen fixation, direct microscopic visualization of bacteria on seedling surfaces to visualize the bacterial oxidation process, reactive oxygen probes to test for the presence of H2O2 and cultural experiments to assess conditions under which H2O2 is secreted by seedlings. We also made surveys of the seedlings of several grass species to assess the distribution of the phenomenon of microbial oxidation in the Poaceae. Key elements of the proposed mechanism for nitrogen acquisition in seedlings include: 1) diazotrophic bacteria are vectored on or within seeds; 2) at seed germination bacteria colonize seedling roots and shoots; 3) seedling tissues secrete ROS onto bacteria; 4) bacterial cell walls, membranes, nucleic acids, proteins and other biological molecules are oxidized; 5) nitrates and/or smaller fragments of organic nitrogen-containing molecules resulting from oxidation may be absorbed by seedling tissues and larger peptide fragments may be further processed by secreted or cell wall plant proteases until they are small enough for transport into cells. Hydrogen peroxide secretion from seedling roots and bacterial oxidation was observed in several species in subfamily Pooideae where seeds possessed adherent paleas and lemmas, but was not seen in grasses that lacked this feature or long-cultivated crop species
Occultocarpon, a new monotypic genus of Gnomoniaceae on Alnus nepalensis from China
Microfungi in the Gnomoniaceae (Diaporthales, Ascomycetes) comprise species commonly reported as pathogens and endophytes on trees and herbaceous hosts primarily from temperate forests of North America, Europe, and Japan. The diversity of Gnomoniaceae in China is poorly known, although several plant families that occur there specifically the Betulaceae are considered important hosts. An exploratory trip to Yunnan, China, resulted in the discovery of several members of the Gnomoniaceae. In this paper a new monotypic genus, Occultocarpon and its species, O. ailaoshanense, are described and illustrated. A phylogeny based on three genes (LSU, rpb2, tef1-α) reveals that O. ailaoshanense belongs to the Gnomoniaceae and forms a branch distinct from the currently known genera. Occultocarpon ailaoshanense is characterized by perithecia with thin, central to eccentric necks in groups embedded in a stroma and oblong elliptical-elongated, one-septate ascospores. Occultocarpon ailaoshanense occurs on the bark of branches of Alnus nepalensis (Betulaceae) in Yunnan, ChinaMicrofungi in the Gnomoniaceae (Diaporthales, Ascomycetes) comprise species commonly reported as pathogens and endophytes on trees and herbaceous hosts primarily from temperate forests of North America, Europe, and Japan. The diversity of Gnomoniaceae in China is poorly known, although several plant families that occur there specifically the Betulaceae are considered important hosts. An exploratory trip to Yunnan, China, resulted in the discovery of several members of the Gnomoniaceae. In this paper a new monotypic genus, Occultocarpon and its species, O. ailaoshanense, are described and illustrated. A phylogeny based on three genes (LSU, rpb2, tef1-α) reveals that O. ailaoshanense belongs to the Gnomoniaceae and forms a branch distinct from the currently known genera. Occultocarpon ailaoshanense is characterized by perithecia with thin, central to eccentric necks in groups embedded in a stroma and oblong elliptical-elongated, one-septate ascospores. Occultocarpon ailaoshanense occurs on the bark of branches of Alnus nepalensis (Betulaceae) in Yunnan, Chin
Five High-Redshift Quasars Discovered in Commissioning Imaging Data of the Sloan Digital Sky Survey
We report the discovery of five quasars with redshifts of 4.67 - 5.27 and
z'-band magnitudes of 19.5-20.7 M_B ~ -27. All were originally selected as
distant quasar candidates in optical/near-infrared photometry from the Sloan
Digital Sky Survey (SDSS), and most were confirmed as probable high-redshift
quasars by supplementing the SDSS data with J and K measurements. The quasars
possess strong, broad Lyman-alpha emission lines, with the characteristic sharp
cutoff on the blue side produced by Lyman-alpha forest absorption. Three
quasars contain strong, broad absorption features, and one of them exhibits
very strong N V emission. The amount of absorption produced by the Lyman-alpha
forest increases toward higher redshift, and that in the z=5.27 object (D_A ~
0.7) is consistent with a smooth extrapolation of the absorption seen in lower
redshift quasars. The high luminosity of these objects relative to most other
known objects at z >~ 5 makes them potentially valuable as probes of early
quasar properties and of the intervening intergalactic medium.Comment: 13 pages in LaTex format, two postscirpt figures. Submitted to the
Astronomical Journa
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Challenges of Profile Likelihood Evaluation in Multi-Dimensional SUSY Scans
Statistical inference of the fundamental parameters of supersymmetric
theories is a challenging and active endeavor. Several sophisticated algorithms
have been employed to this end. While Markov-Chain Monte Carlo (MCMC) and
nested sampling techniques are geared towards Bayesian inference, they have
also been used to estimate frequentist confidence intervals based on the
profile likelihood ratio. We investigate the performance and appropriate
configuration of MultiNest, a nested sampling based algorithm, when used for
profile likelihood-based analyses both on toy models and on the parameter space
of the Constrained MSSM. We find that while the standard configuration is
appropriate for an accurate reconstruction of the Bayesian posterior, the
profile likelihood is poorly approximated. We identify a more appropriate
MultiNest configuration for profile likelihood analyses, which gives an
excellent exploration of the profile likelihood (albeit at a larger
computational cost), including the identification of the global maximum
likelihood value. We conclude that with the appropriate configuration MultiNest
is a suitable tool for profile likelihood studies, indicating previous claims
to the contrary are not well founded.Comment: 21 pages, 9 figures, 1 table; minor changes following referee report.
Matches version accepted by JHE
Cognitive behaviour therapy versus counselling intervention for anxiety in young people with high-functioning autism spectrum disorders: a pilot randomised controlled trial
The use of cognitive-behavioural therapy (CBT) as a treatment for children and adolescents with autism spectrum disorder (ASD) has been explored in a number of trials. Whilst CBT appears superior to no treatment or treatment as usual, few studies have assessed CBT against a control group receiving an alternative therapy.
Our randomised controlled trial compared use of CBT against person-centred counselling for anxiety in 36 young people with ASD, ages 12â18. Outcome measures included parent- teacher- and self-reports of anxiety and social disability.
Whilst each therapy produced improvements inparticipants, neither therapy was superior to the other to a significant degree on any measure. This is consistent with findings for adults
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